Field
The present invention relates to a semiconductor device including a diode structure for a power semiconductor.
Background
In a diode for a power semiconductor, a contact hole in a main cell region is filled with a thick AlSi electrode in order to cause a large current to flow vertically. Also, a field limiting ring (FLR) structure is adopted as a terminal structure, and field plate (FP) electrodes are formed on a guard ring (GR) and field limiting rings (FLRs), thereby enabling a depletion layer to extend easily (see, for example, JP 09-023016 A). Further, a semi-insulating protective film is formed on the entire surface of the terminal region for the purpose of stabilizing the potential.
In recent years, there has been a trend to replace wire bonding (WB) with direct lead bonding (DLB) as a method of joining a region for causing a current to flow through a main cell region. Therefore, there have been increasing cases where an electrode for soldering is formed on a main electrode.
In recent years, a need has arisen to make a terminal region finer in order to reduce an ineffective region even in power semiconductors. However, a fine pattern cannot be formed because the film thicknesses of electrodes are large. Even if a fine pattern having a large difference in height and a high aspect ratio can be formed, an electrode fall-down or a crack in a protective film at an electrode step portion is caused by stress from an external package, resulting in a reduction in reliability. On the other hand, making the electrode in the main cell region excessively thin leads to breakdown due to local current concentration, a disconnection due to degradation of coverage at a contact end portion and damage to the Si substrate at the time of forming electrodes to which external electrodes are to be soldered. Thus, there is a problem of failure to realize high reliability.